Methylthio yeasts

Examination of 37 basidiomycetous yeasts indicated formation of several sulfur volatiles 3-(methylthio)-l-propanol, methanethiol (MT), S-methyl thio-acetate, dimethyl disulfide (DMDS), dimethyl trisulfide (DMTS), allyl methyl sulfide and 4,5-dihydro-3(2//)-thiophenone. The component produced in the largest amounts, 40 100 mg L-1, was 3-(methylthio)-l-propanol29 Cheeseripening yeasts are considered later (Section 11.1.2.4.5). 

In contrast, the latter. ryw-isomer, ethyl (TS,2R)-2-(1 -hydroxymethyl)-4-pentenoate. was recently prepared as the only product of a reduction with an enzyme fraction obtained from baker s yeast176. Introduction of a sulfur-containing functional group into the substrate increases stereocontrol in baker s yeast reduction of many ketonesI2e>. 2-Methylthio-3-keto esters are selectively reduced to the (3S)-3-hydroxy esters (Table 5)123,127. The 2-methylthio group is easily removed by 3-chloroperbenzoic acid oxidation to the corresponding sulfoxide followed by subsequent reduction with aluminum-mercury amalgam. Thus, these compounds can also be used for the preparation of optically pure 2-unsubstituted 3-hydroxy esters. 

De Kimpe N.G. and Aelterman W.A. (1996) Synthesis of 2- [(methylthio)methyl] -2-butenal, a characteristic flavor component of potato chips, krill seasoning, roasted coffee, and yeast extracts, J. Agric. Food Chem. 44, 3598-3600. 

Two other low volatile sulfur compounds included in this study were 2-methylthio-l-ethanol (MTE) and 3-methylthio-l-p>rop>anol or methionol (MTP). MTP is considered to be the most important heavy sulfur compound involved with reduction defects brought about by yeast activity (Ribereau-Gayon et al., 2006b). MTP can generate odours reminiscent of cauliflower and cabbage at a concentration above its perception threshold (1200 pg/L). MTE... 

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